6.4.2 Homeostasis : control of blood glucose concentration Flashcards
Describe the factors that influence blood glucose concentration
● Consumption of carbohydrates → glucose absorbed into blood
● Rate of respiration of glucose eg. increases during exercise due to muscle contraction
Describe the role of the liver in glycogenesis,
glycogenolysis and gluconeogenesis
Glycogenesis: Converts glucose → glycogen
Glycogenolysis: Converts glycogen → glucose
Gluconeogenesis: Converts amino acids and/or
glycerol → glucose
Explain the action of insulin in decreasing blood glucose concentration
● Attaches to specific receptors on cell surface membranes of target cells eg. liver / muscles
1. This causes more glucose channel proteins to join cell surface membrane
○ Increasing permeability to glucose
○ So more glucose can enter cell by facilitated diffusion
2. This also activates enzymes involved in glycogenesis
○ Lowering glucose concentration in cells, creating a concentration gradient
○ So glucose enters cell by facilitated diffusion
Explain the action of glucagon in increasing blood glucose concentration
● Attaches to specific receptors on cell surface membranes of target cells eg. liver
1. Activates enzymes involved in glycogenolysis
2. Activates enzymes involved gluconeogenesis
● This establishes a concentration gradient → glucose enters blood by facilitated diffusion
Explain the role of adrenaline in increasing blood glucose concentration
Fear / stress / exercise → adrenal glands secrete adrenaline:
● Attaches to specific receptors on cell surface membranes of target cells eg. liver
● Activates enzymes involved in glycogenolysis
● This establishes a concentration gradient → glucose enters blood by facilitated diffusion
Describe the second messenger model of adrenaline and glucagon action
- Activates enzyme adenylate cyclase (changes shape)
- Which converts many ATP to many cyclic AMP (cAMP)
- cAMP acts as the second messenger → activates protein kinase enzymes
- Protein kinases activate enzymes to break down glycogen to glucose
Suggest an advantage of the second messenger model
● Amplifies signal from hormone
● As each hormone can stimulate production of many molecules of second messenger (cAMP)
● Which can in turn activate many enzymes for rapid increase in glucose
Compare the causes of types I and II diabetes
Both - higher and uncontrolled blood glucose concentration; higher peaks after meals and remains high
Type 1
● Key point = β cells in islets of langerhans
in pancreas produce insufficient insulin
● Normally develops in childhood due to
an autoimmune response destroying β
cells of Islets of Langerhans
Type 2
● Key point = receptor (faulty) loses responsiveness /
sensitivity to insulin (but insulin still produced)
● So fewer glucose transport proteins → less uptake of
glucose → less glycogenisis
● Risk factor = obesity
Describe how of type I diabetes can be controlled
● Injections of insulin (as pancreas doesn’t produce enough)
● Blood glucose concentration monitored with biosensors; dose of insulin matched to glucose intake
● Eat regularly and control carbohydrate intake eg. those that are broken down / absorbed slower
○ To avoid sudden rise in glucose
Suggest why insulin can’t be taken as a tablet by mouth
● Insulin is a protein
● Would be hydrolysed by endopeptidases / exopeptidases
Describe how of type II diabetes can be controlled
● may use drugs targeting insulin receptors to increase sensitivity
○ To increase glucose uptake by cells / tissues
● Reduce sugar intake (carbohydrates) → less absorbed
● Reduce fat intake → less glyconeogenisis
● More (regular) exercise → uses glucose / fats by increasing respiration
● Lose weight → increased sensitivity of receptors to insulin
Describe how you can evaluate the positions of health advisers and the food
industry in relation to the increased incidence of type II diabetes
● Health advisers aim - reduce risk of type II diabetes due to health problems caused (eg. kidney failure)
○ So need to reduce obesity as it is a risk factor
● Food industry aim - maximise profit
